Title Science and Technology Indonesia e-ISSN:2580-4391 p-ISSN:2580-4405 Vol. 4, No. 3, July 2019 Research Paper Removal of Anionic Direct Dye Using Zn/Al, Zn/Fe and Zn/Cr Layered Double Hydroxides Toward Interlayer Distance Neza Rahayu Palapa1, Tarmizi Taher2, Risfidian Mohadi1,2, Aldes Lesbani1,2* 1Magister of Chemistry, Faculty of Mathematics and Natural Sciences, Sriwijaya University, Jl.. Padang Selasa Bukit Besar Palembang 30139 2Department of Enviromental Science, Graduate School, Sriwijaya University, Jl. Padang Selasa No. 524 Ilir Barat 1, Palembang-South Sumatra, Indonesia *Corresponding author: aldeslesbani@pps.unsri.ac.id Abstract In order to minimize harmful e�ect of synthetic dye (direct yellow and direct violet) the capacity of Zn/Al, Zn/Cr and Zn/Fe layered double hydroxides of these contaminant was studied in this work. Batch adsorption experiment was conduct to investigate the e�ect of various operating parameters such as contact time, initial dye concentration and adsorption temperature in order to provide optimal condition in removal synthetic dye. Based on result, the sorption of direct dye onto LDHs followed pseudo-second-order rate model. The equilibrium adsorption data for both direct dye was fi�ed Freundlich isotherm model. Keywords adsorption, synthetic dye, layered double hydroxide, kinetic, thermodynamic Received: 21 June 2019, Accepted: 18 July 2019 https://doi.org/10.26554/sti.2019.4.3.70-76 1. INTRODUCTION Water is the most important for all living organism, develop- ment and also the environment (Gu et al., 2018). Unfortunately, now days water source has been containing many pollutants (Faust and Aly, 2018). Its caused by many industries doesn’t care about waste, they throwing away their waste in water irrigation, a small river and also in pond retention (Faust and Aly, 2018). That’s why water treatment become a serious problem environ- ment and also many researchers are search the e�ective ways to get clean water (Guimares et al., 2019; Boubakri et al., 2018; Palapa et al., 2018). However, rapidly demand new and diverse products based on technology in�uences many industries more prepared to using synthetic chemicals (Ke�f et al., 2019), which is increasing the pollutant and harmful to human and environment (Oladipo et al., 2019). Nowadays, almost 78% of industries such as textile, paper, leather, paints, food and also cosmetics are using synthetic dyes (Faust and Aly, 2018; Marzbali et al., 2017). In the large scale, syn- thetic dye continuously causing environmental water gets worse (Taher et al., 2019b). Indeed the presence of these substances in the aquatic environment reduces the oxygen and disturbs the biological cycle of aquatic biota (Taher et al., 2019b; Ke�f et al., 2019). Moreover, the presence of a pollutant in drinking water is more dangerous to human, its can caused reproductive system disorder, caused cancer liver, brain, mutagenic and car- cinogenic (Palapa et al., 2018; Saria et al., 2018; Faust and Aly, 2018). Generally, many textile industries used direct dye, due to their excellent binding ability (Boubakri et al., 2018). Removal the pollutant into wastewater has been studied tak- ing the e�ciency and cost, various methods such as biological treatment (Faust and Aly, 2018), membrane �ltration (Xiao et al., 2019), electrochemical, photochemical (Zhu et al., 2018), coagu- lation (Huang et al., 2019), degradation and adsorption (Taher et al., 2019a). Most of them have high cost and not easy to op- eration, except, adsorption. The adsorption process has widely used, easy to operation, low cost and high e�ectiveness water treatment. In fact, the main weakness of the adsorption method is the high cost and impurity of the conventional sorbent. Hence, cheaper and e�ective sorbent is still required to solve this prob- lem (Miandad et al., 2018). Now, researchers have been focused on the development of natural clays. Layered double hydroxides are the one of synthetic clay mineral which has ability to removal various contaminant from aqueous solution. Layered double hydroxides (LDHs) has consist of brucite layers by metal cation divalent and trivalent substi- tuted (Palapa et al., 2019). Generally, LDHs has formula [M2+(1- x)M3+x(OH)2](An-)x/nH2O, (denoted as M 2+ and M3+ , where M2+ is a divalent metal cation, such as Mg2+, Fe2+, Co2+, Cu2+, Ni2+, Ca2+, and M3+ is a trivalent metal cation, such as Al3+, Cr3+, Ga3+, Mn3+ or Fe3+. LDHs has unique structure proper- ties favorable for adsorption of dye, which is they have speci�c features like no toxic, anion exchange properties, good thermal stability, has high �exibility, high surface area, and easy to han- https://doi.org/10.26554/sti.2019.4.3.70-76 Palapa et. al. Science and Technology Indonesia, 4 (2019) 70-76 Figure 1. XRD Pattern of Zn/Al, Zn/Cr and Zn/Fe LDHs Figure 2. FTIR Spectra of Zn/Al, Zn/Cr and Zn/Fe LDHs dling (Taher et al., 2019a; Palapa et al., 2019; Boubakri et al., 2018; Nidheesh et al., 2018; Tajuddin et al., 2018). In this work, LDHs was made to study of removal ability direct dye onto LDHs from aqueous solution. LDHs has been pre- pared by co-precipitation method and characterized using XRD, FTIR and Surface Area Analyses by BET method. the adsorption factors performance such as time, initial dye concentration and temperature was investigated. Sorption capacity was studied using kinetic laws and isotherm models. 2. EXPERIMENTAL SECTION 2.1 Materials The chemical used in this experiment are analytical grade, such as zinc nitrate, aluminum nitrate, iron nitrate, chromium nitrate and also sodium nitrate was purchased by Merck, dyes were obtained in local textile industry in Palembang and the water was used as solvent was obtained by purifying water de-ionized Figure 3. Isotherm Graphic adsorption-desorption of (a) Zn/Al, (b) Zn/Cr and (c) Zn/Fe LDHs ‘Purite’. LDH was characterized using a Rigaku Mini�ex 600, Shimadzu Prestige-21 and BET (ASAP Micromeritics 2020). 2.2 Methods 2.2.1 Synthesis of Layered Double Hydroxide According to Palapa et al. (2019), the synthesis of layered double hydroxide was conducted to alkaline precipitation with divalent and trivalent metal cation ratio 3:1 at nitrogen atmosphere. Pre- pare the alkaline solution for zinc nitrate (0.75 M), aluminum nitrate (0.25 M), chromium nitrate (0.25 M) and also iron nitrate (0.25 M). divalent and trivalent metal cation are mixed as long as an hour and added to 50 mL of sodium hydroxide (2 M) with continuous stirring 240 rpm for 4 hours at 60 ºC. then the so- lution was adjusted at pH 10 using sodium hydroxide and let the mixing solution at 60 ºC overnight. After that, the solution kept in oven at 80 ºC until we obtain gel, then LDH was �ltered, washed for several times using de-ionized water and �nally dried at 60 ºC for 24 h. The obtained solid then keep in a sealed bottle and ready for further used as an adsorbent. 2.2.2 Adsorption Experiment As much as 0.05 g of adsorbent was added to 50 mL of dyes solution in a certain concentration, in this work we used direct yellow and direct violet dye as the adsorbate. The dye solution was prepared by 1 g of each dye were diluted into 1000 mL (as stock solution) then dissolve gradually. Then 0.05 g adsorbent added into 50 mL adsorbate and shaken with speci�ed time at 240 rpm. After that, the solution was �ltered and the �nal concentration was calculated using UV-Vis spectrophotometer. 3. RESULTS AND DISCUSSION 3.1 Adsorbent Characterization Zn/Al, Zn/Cr and Zn/Fe layered double hydroxides (LDHs) were successfully prepared and each LDHs were characterized by XRD, FT-IR and Surface Area Analyses. The result of X-ray Di�raction was shown in Fig. 1. The pattern was shown the unique di�raction of LDHs amount 10º, 22º, 30º, 35º, 49º and overlapping peaks at 60º are characterized by LDHs. For all LDHs, the sharp peaks at amount 10o were indicated interlayer of LDHs with higher distance is Zn/Al 7.57 Å, Zn/Cr 7.32 Å and Zn/Fe 5.80 Å. Then all of LDHs has been characterized using FT- IR and the spectra were shown in Fig 2. Zn/Al, Zn/Cr and Zn/Fe spectra have identically vibration were indicating nitrate band, OH band and M-O band. All identical spectra were shown in Fig © 2019 The Authors. Page 71 of 76 Palapa et. al. Science and Technology Indonesia, 4 (2019) 70-76 Figure 4. E�ect of contact time adsorption (a) direct yellow and (b) direct violet onto layered double hydroxides (LDHs) Figure 5. E�ect of initial concentration of (a) direct yellow dye and (b) direct violet dye onto LDHs at various temperature 2. amount 3400-3600 cm−1 for OH band, a vibration of nitrate anions at 1380 cm−1 and vibration under 1000 cm−1 generally indicate M-O band. According to Boubakri et al. (2018); Taher et al. (2019a), lay- ered double hydroxides has much potential application its be- cause layered double hydroxides have unique structure as layer materials which is interlayer easily to exchangeable. So, in this work, LDHs were characterized by surface area analyses by BET method. the result of each LDHs shows in Fig 3 and Table 1. Fig. 3 were shows the curve of adsorption and desorption of Zn/Al, Zn/Cr and Zn/Fe LDH, respectively. The typical nitrogen adsorption-desorption isotherms and the corresponding pore size distribution and the Fig. 3 indicating Zn/Al, Zn/Cr and Zn/Fe LDHs have mesoporous pore. Table 1. Listed the volume pore and pore size based on digital data of characterization. Accord- ing to IUPAC, diameter pore of material such as micropore has pore <2 nm, mesopore between 2-50 nm and macropore >50 nm. Table 1. Data of volume pore and pore size of layered double hydroxides Adsorbent SBET Volume Pore Pore Size (m2/g) (BJH, cm3 /g) (�, nm) Zn-Al-NO3 9.4128 0.045351 19.2743 Zn-Fe-NO3 2.8834 0.010334 14.6964 Zn-Cr-NO3 11.865 0.112128 3.77051 3.2 Adsorption Study 3.2.1 Kinetic Adsorption Study E�ect of adsorption time of direct dyes by Zn/Al, Zn/Cr and Zn/Fe LDHs was shown in Fig. 4. The adsorption process of direct dye onto layered double hydroxides was setting up at room temperature and 100 mg/L adsorbate for each LDHs. The result of adsorption was calculated using UV-Vis Spectropho- tometer is the �nal concentration at 403 nm and 549 nm. After that, we calculated the % adsorbed, then we identify the kinetic parameters adsorption process. The maximum adsorption time direct yellow onto Zn/Al, Zn/Cr and Zn/Fe LDHs at an hour with % adsorbed are amount 83%, 81% and 38%, respectively. However the adsorption direct violet onto Zn/Al, Zn/Cr and Zn/Fe LDHs have maximum adsorption time at an hour amount 71%, 49% and also 27%, respectively. Based on result, layered double hydroxides more e�ective to adsorb direct yellow dye than direct violet dye. In this work, we �tted two kinetic models. i.e. pseudo-�rst-order and pseudo-second-order. These kinetic models equation as follows: Pseudo-�rst-order: log(Qe − Qt) = logQe − k1/(2.303)t (1) and pseudo-second-order: t/Qt = (1/k2Qe2) + (1/Qe)t (2) where qe and qt are capacities of adsorbed (mg.g−1), t is time adsorption process, k1is the rate constant of the �rst order and k2 the rate constant of second-order. Table 2. Shows the data of kinetic parameters of direct dyes adsorption onto LDHs. Based on coe�cient correlation of direct dye adsorption onto layered double hydroxides was followed pseudo-second-order kinetic model. Generally, the adsorption of dye onto LDHs is quite rapidly initially until the equilibrium was reached and the value of adsorbed are constant. Its caused, active site of layered double hydroxides at equilibrium are full than before reached equilibrium which is the surface active site is more available. 3.2.2 Isotherm and Thermodynamic Study The thermodynamic was studied by varying initial concentra- tion and temperature. In Figure 5, dye adsorbed is higher at temperature 343 K so that the interaction of adsorbate and adsor- bent are higher than solvent-adsorbent at active site adsorption. Therefore, the adsorption for both direct dye onto LDHs at vary- ing temperature were shown in Fig. 5. Fig 5 were shows the e�ect of initial concentration at various temperature. The higher adsorption capacity of both dyes (direct yellow and direct violet) is Zn/Al layered double hydroxides at 323 K it’s amount 98 mg/g and 36 mg/g, respectively. The isotherms models Langmuir and Freundlich are used for this data. The Langmuir assumed that adsorbate was occupied into monolayer. Its used equation as follows: Ce/Qe = 1/(KLQmax) + (1/Qmax)Ce (3) © 2019 The Authors. Page 72 of 76 Palapa et. al. Science and Technology Indonesia, 4 (2019) 70-76 Table 2. Pseudo-�rst-order and pseudo-second-order sorption rate constant kinetic models. Kinetic models Dye Parameters Layered double hydroxides Zn-Al-NO3 Zn-Cr-NO3 Zn-Fe-NO3 Pseudo-�rst-order Direct Yellow k1 0.0597 0.0493 0.0339 R2 0.9127 0.873 0.891 Pseudo-second-order k2 0.0064 0.005 0.0072 R2 0.9544 0.9077 0.9176 qe exp 80.791 84.565 54.965 Pseudo-�rst-order Direct Violet k1 0.0414 0.0364 0.0339 R2 0.938 0.922 0.912 Pseudo-second-order k2 0.004 0.0045 0.0072 R2 0.9297 0.9883 0.948 qe exp 75.791 62.012 44.056 Table 3. Langmuir and Freundlich Isotherm Model Fitted for adsorption direct yellow onto LDHs Adsorbent Isoterm Parameters T (K) 303 313 323 Zn/Al Langmuir qmax (mg.g-1) 100.706 118.7815 121.3768 kL (Lmg−1) 0.009 0.0328 0.0515 R2 0.6023 0.7954 0.905 Freundlich kF (mg.g−1)(Lmg−1)1/n 3.5136 13.506 19.5108 n 1.3646 2.3814 2.6625 R2 0.9025 0.9045 0.9363 Zn/Cr Langmuir qmax (mg.g-1) 86.4756 91.1563 104.3262 kL (Lmg−1) 0.0052 0.0041 0.0033 R2 0.6999 0.992 0.9855 Freundlich kF (mg.g−1)(Lmg−1)1/n 1.8634 1.788 1.8525 n 1.2733 1.183 1.133 R2 0.9734 0.998 0.9986 Zn/Fe Langmuir qmax (mg.g−1) 39.654 39.2063 32.8447 kL (Lmg−1) 0.034 0.0228 0.0443 R2 0.6075 0.89 0.9793 Freundlich kF (mg.g−1)(Lmg−1)1/n 0.1918 1.7759 2.4524 n 0.7738 1.5642 1.6492 R2 0.9699 0.9081 0.9848 © 2019 The Authors. Page 73 of 76 Palapa et. al. Science and Technology Indonesia, 4 (2019) 70-76 Table 4. Langmuir and Freundlich Isotherm Model Fitted for adsorption direct violet onto LDHs Adsorbent Isoterm Parameters T (K) 303 313 323 Zn/Al Langmuir qmax (mg.g−1) 39.654 45.2025 66.093 kL (Lmg−1) 0.1472 0.1246 0.0387 R2 0.9808 0.9473 0.998 Freundlich kF (mg.g−1)(Lmg−1)1/n 20.5059 20.6027 9.1501 n 7.4144 6.189 2.5095 R2 0.9902 0.9942 0.998 Zn/Cr Langmuir qmax (mg.g−1) 37.6209 56.7362 47.5136 kL (Lmg−1) 0.0122 0.0099 0.0239 R2 0.9202 0.7694 0.9839 Freundlich kF (mg.g−1)(Lmg−1)1/n 1.6529 1.5044 4.6399 n 1.8141 1.544 2.2851 R2 0.9621 0.902 0.987 Zn/Fe Langmuir qmax (mg.g-1) 23.709 28.332 31.095 kL (Lmg−1) 0.0071 0.0046 0.0409 R2 0.847 0.713 0.829 Freundlich kF (mg.g−1)(Lmgg−1)1/n 2.604 6.882 9.571 n 1.303 1.265 2.507 R2 0.992 0.949 0.906 Table 5. Values of Thermodynamic Parameters for The Adsorption of Direct Yellow By LDHs T C Zn/Al LDH Zn/Cr LDH Zn/Fe LDH (K) (mg/L) ΔG ΔS ΔH ΔG ΔS ΔH ΔG ΔS ΔH (kJ/mol) (J/mol.K) (kJ/mol) (kJ/mol) (J/mol.K) (kJ/mol) (kJ/mol) (J/mol.K) (kJ/mol) 303 60 -1.049 64.961 18.634 -2.975 39,00 9,819 -0,989 32,01 8,71 313 -2.348 -5.714 -1,282 323 -3.647 -0.009 -1,575 303 70 -0.199 45.216 13.501 -2.18 39,75 5,223 -0,990 26,47 4,50 313 -1.104 -4.351 -1,631 323 -2.008 -0.227 -2,271 303 80 -0.245 46.498 13.844 -2.975 35,59 9,650 -1,355 17,879 7,35 313 -1.175 -5.714 -1,742 323 -2.105 -0.009 -2,129 303 90 -0.378 30.336 8.814 -2.18 47,50 9,311 -0,838 11,06 1,96 313 -0.984 -4.351 -1,379 323 -1.591 -0.227 -1,920 303 100 -0.831 28.635 7.093 -0.009 33,402 6.991 -0.012 12.3543 3.889 313 -2.075 -2.18 -1.05 323 -3.318 -4.351 -2.087 © 2019 The Authors. Page 74 of 76 Palapa et. al. Science and Technology Indonesia, 4 (2019) 70-76 Table 6. Values of Thermodynamic Parameters for The Adsorption of Direct Violet By LDHs T C Zn/Al LDH Zn/Cr LDH Zn/Fe LDH (K) (mg/L) ΔG ΔS ΔH ΔG ΔS ΔH ΔG ΔS ΔH (kJ/mol) (J/mol.K) (kJ/mol) (kJ/mol) (J/mol.K) (kJ/mol) (kJ/mol) (J/mol.K) (kJ/mol) 303 60 -1.049 64.961 18.634 -2.975 39,00 9,819 -0,989 32.01 8.71 313 -2.348 -5.714 -1,282 323 -3.647 -0.009 -1,575 303 70 -0.199 45.216 13.501 -2.18 39,75 5,223 -0,990 26.47 4.5 313 -1.104 -4.351 -1,631 323 -2.008 -0.227 -2,271 303 80 -0.245 46.498 13.844 -2.975 35,59 9,650 -1,355 18 7.35 313 -1.175 -5.714 -1,742 323 -2.105 -0.009 -2,129 303 90 -0.378 30.336 8.814 -2.18 47,50 9,311 -0,838 11.06 1.96 313 -0.984 -4.351 -1,379 323 -1.591 -0.227 -1,920 303 100 -0.831 28.635 7.093 -0.009 33,402 6.991 -0.012 12.3543 3.889 313 -2.075 -2.18 -1.05 323 -3.318 -4.351 -2.087 Where qe is the equilibrium adsorption, Ce is equilibrium concentration, qmax is the maximum adsorption and kL is the equilibrium adsorption constant. Then, the essential features of Langmuir isotherm namely RL (equilibrium parameters). Value RL has indicated the models of isotherm. If irreversible, the RL calculated zero (RL = 0), liniear when RL = 1, and favorable when 0> RL>1. The Freundlich isotherm model identi�ed the heterogenous adsorbent surface. The equation is following: Logqe = LogkF + nLogCe (4) Where kF is adsorption capacity when equilibrium, the value of n gives information of favorability of adsorption process, if n=1 linear, n<1 is chemisorption and n>1 is favorable. The isotherm data were shown in Table 3. Tabel 3 was shown the parameters of Freundlich and Langmuir. The result was shows Freundlich model is more �tted of the experimental data based on coe�cient correlation. This result indicated the adsor- bate interact physisorption each other on surface site active of layered double hydroxides. Thermodynamic study parameter was calculated and obtained enthalpy, entrophy and free Gibbs Energy. The value of enthalphy and entrophy shows that the adsorption process is endothermic. Negative free energy value was indicated that the process is spontaneous and the desreases of free energy value with the increases of temperature indicated that the adsorption more favorable at low temperature (room temperature). 4. CONCLUSIONS In this work, Zn/Al, Zn/Cr and Zn/Fe has been used as adsorbent for removal dyes in aqueous solution. Based on result, Zn/Al LDHs has higher adsorption capacity than Zn/Cr and Zn/Fe LDHs. For removal direct dyes, LDHs more e�ective adsorb direct yellow dye than direct violet dye. Kinetics study showed that the adsorption process is more �ts with PSO than PFO based correlation coe�cients. The adsorption process is described by Freundlich isotherm models for all dyes. The value of enthalpy and entropy shows that the adsorption process is endothermic and negative free energy value was indicated that the process is spontaneous. 5. 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Page 76 of 76 INTRODUCTION EXPERIMENTAL SECTION Materials Methods Synthesis of Layered Double Hydroxide Adsorption Experiment RESULTS AND DISCUSSION Adsorbent Characterization Adsorption Study Kinetic Adsorption Study Isotherm and Thermodynamic Study CONCLUSIONS ACKNOWLEDGEMENT